THE PLOT
After finally finding a balance between being Spider-Man, and spending time with Mary Jane Watson, who has become a Broadway actress, Peter Parker begins to feel secure in his life. One night, a meteorite crash-lands in a park near where Peter and Mary Jane are on a date. The meteor contains a black, alien symbiote, which hitches a ride home with Peter on his moped. Feeling good about his relationship, Peter sets plans to marry Mary Jane, and Aunt May gives him her engagement ring so that he can do it properly.
Harry Osborn, crafting a new glider, and using the performance enhancing drugs from Oscorp, seeks vengeance for his father's death, which he believes Peter caused. A battle between the two former friends leaves Harry with short-term amnesia, and with no more anger toward Peter. Flint Marko, recently escaped from prison, stumbles into a particle accelerator filled with sand. The machine changes Marko's DNA, transforming his body into sand. During a festival honoring Spider-Man, Marko attempts to rob an armored car. Spider-Man shows up, but Marko is too much for him to handle. Later, Captain Stacey informs Peter and Aunt May that Flint Marko is the one that killed Ben Parker. Seeking revenge of his own, Peter waits Marko to strike again. Waiting till Peter is asleep, the symbiote bonds with his costume. Peter finds that, not only has his costume changed, but that his powers have been enhanced too.
The black suit brings out Peter's more violent and vengeful side, as he seemingly kills Marko after a battle in a subway tunnel. The darker side of the suit begins to transform Peter's personality as well, causing him to expose a new photographer at the Daily Bugle, Eddie Brock, Jr., as a fraud, while stealing his girlfriend, Gwen Stacy. His behavior causes him to push Mary Jane away, and she finds solace in Harry Osborn. Harry soon recovers from his amnesia and lures Peter into his mansion to kill him. Harry is left permanently scarred when Peter throws a pumpkin bomb at him.
After accidentally physically hurting Mary Jane, Peter decides to get rid of the black suit. He goes to a church tower to remove the black suit. The noise from the bell allows him to rip the suit off, which starts fighting its removal. Coincidentally, a humiliated Brock goes to the same church and prays for God to kill Peter Parker, before overhearing Peter in the bell tower. Entering to investigate, Eddie sees Peter, unmasked as Spider-Man. The symbiote falls from the tower and lands on Brock. After being mistaken for Spider-Man, Brock propositions Marko, who is still alive, and claims that they should unite to destroy Spider-Man.
Brock kidnaps Mary Jane and uses her as bait to lure Peter to a construction site. Peter approaches Harry for help, but Harry refuses. Spider-Man arrives on the scene and is brutally beaten by Marko, until Harry, who learns his father did kill himself, arrives and rescues Peter. Harry and Peter team up against Brock and Marko. As the fight progresses, Eddie grabs Harry's glider and lunges at Peter; Harry jumps in front of Peter and the glider impales him instead. Peter attempts to free Eddie of the black symbiote, clanging pipes together to weaken it. However, Eddie has grown too attached to the power the symbiote provides, and attempts to reattach himself to the symbiote just as Peter throws a pumpkin bomb at it; Eddie and the symbiote appear to die in the explosion. Marko tells Peter that he had no intention of killing Ben Parker, but that it was an accident caused by fear and desperation. Peter forgives Flint, who breaks apart and floats away in the breeze. Harry does not survive his wounds and dies with Mary Jane and Peter by his side. Peter and Mary Jane revive their relationship, after attending their friend's funeral.